The original goals of the first three years of this Clinical Investigator Award were: 1) to define the organelles that regulate intracellular calcium homeostasis in chondrocytes from various zones of the growth plate, 2) to study the effects of parathyroid hormone, calcitonin, somatomedins and the vitamin D3 metabolites on intracellular ionized calcium, 3) to study the effect of hypoxia on calcium regulation in the growth plate chondrocyte. During the first two years of funding (1984-1986) I completed the first two of these objectives and obtained additional funding to complete the design and manufacture of specialized equipment of begin the study of the third objective. During the third year of this award (1986-1987), I plan to complete the preliminary study and equipment calibration necessary to study the effect of hypoxia on intracellular calcium homeostasis in the growth plate chondrocyte. During the two years of funding requested in this grant renewal (1987-1989) the first goal will be to complete the study of hypoxia on intracellular calcium transport. During the 1988-1989 funding year, we will use a technique of high voltage electric fields to nondestructively permeabilize the plasma membrane in order to manipulate the intracellular ionized calcium concentration and study the effect of increased (Cai) on matrix vesicle formation and collagen metabolism. During these five year of funding we will accomplish a much more complete understanding of the regulation of intracellular calcium in the growth plate, the effect of the hormonal milieu and microenvironmental hypoxia on intracellular calcium, and the effect on increased intracellular calcium on growth plate chondrocyte metabolism. This data will lead to a better overall understanding of growth plate physiology and specifically define the role of intracellular calcium in growth plate physiology and matrix mineralization. A significant portion of the original proposal has been completed and the preliminary portion of experiments outlined in this proposal are underway. In order to complete this work an additional two years of funding is requested under this Clinical Investigator Award.